Furnaces for the heat processing of products can include one or more heat zones along the length of the furnace, with respective entrance and exit zones at the furnace ends, and one or more intermediate zones between heat zones. The zones can be separated by movable doors, which can be raised to provide for product conveyance between adjacent zones, and which can be closed to isolate the adjacent zones from each other. Different atmospheres and/or temperatures may be provided in respective zones in accordance with particular processes being performed on product transported through the furnace. It is often necessary or desirable that respective zones of the furnace be isolated from adjacent zones in order to accomplish particular processing operations. It is also desirable that the furnace be capable of performing a variety of different processes or process sequences without alteration of the furnace hardware. Furnaces are known in which adjacent zones can be selectively isolated, and these furnaces have employed a walking beam conveyor in the heat zone to convey a product through the heat zone, and a roller or other type of separate conveyor within the adjacent zone which is operative to convey a product in the adjacent zone.